Euler's implicit formula for diff. eqs. - Convergence

Hi good people, I'm doing some old exam questions and here's one I don't quite get.

We have the ordinary diff. eq,

where and .

If we want to solve this by using Euler's implicit formula, we need solve an equation by say fixed-point iteration in each step. How small must the step size be in order for the fixed-point iteration to converge on each step.

First of all, the problem does not say what kind of implicit formula I need to use. I get to the formula in the following manner,

,

and so,

.

To get an implicit formula from this I could simply approximate the integral by,

,

or I could approximate it by the Trapezoidal rule.. Let's assume I do the former such that,

Now I need to use fixed-point iteration to solve this equation. If I let my first guess at be which I believe is a reasonable guess, then I could write this thing in the familiar way;

.

The sequence defined by the expression above converges if for all in the interval. But and so but that doesn't make much sense does it? I don't think the step size must be zero Hope someone can help me out here.